Staffers with Southern California’s air quality agency are proposing a ballot measure that would impose a quarter cent tax to help cut diesel emissions throughout the region.

The proposal, which would begin with a survey of residents, isn’t without critics. They argue that staffers are trying to sidestep the governing board at the South Coast Air Quality Management District by asking residents, directly, if they would be willing to pay the potential tax.

“Taxes should be absolutely the last resort,” said Orange County Supervisor Shawn Nelson, an AQMD board member and congressional candidate in a district that reaches from north Orange County into Los Angeles and San Bernardino counties. “There’s nothing emergency about this.”

The quarter cent sales tax would be a first from the AQMD. It could generate $700 million dollars a year to help electrify transport trucks that carry goods throughout Southern California. The move would be part of a 15-year plan aimed at reducing some of the region’s more dangerous pollutants, ozone and nitrogen oxide.

For decades Southern California has been designated as being in “extreme non-attainment” for ozone levels by the federal government — the worst designation — meaning the region did not hit targets on the amount of pollution in the air.

“We’re making a lot of headway, but it’s a combination of two things,” said the agency’s spokesman Sam Atwood.

“We have the worst smog in the nation for a number of reasons. The second thing is, every year, medical studies show there are harmful effects of ozone at lower levels than were previously known, and standards are made more stringent,” Atwood said.

“We’re making a lot of progress,” he added.

The proposed tax would pay some 70 percent of the projected $1 billion cleanup. It would be used by local businesses to convert older diesel fleet vehicles — which are the region’s top contributor of nitrogen oxide — to green trucks.

The agency isn’t able to regulate emissions from cross-country trucks transporting goods to businesses and many that frequent the port complex, in part, because that is the role of other agencies.

On Monday, the SCAQMD’s legislative committee — which includes five of the agency’s 13-member governing board — voted in favor of polling residents and advancing the proposed tax to legislators. Two local officials, Nelson and San Bernardino County Supervisor Janice Rutherford, objected, saying other options should be explored before resorting to a tax.

“A tax for clean air and projects is not warranted,” Rutherford said, who advocated for expansion of cap and trade programs. “I’m not willing to let the state off the hook. And I’m not willing to support an oppressive tax.”

The governing board could pull the report from the agency’s agenda at its March 2 meeting and halt the agency from getting a legislator to sponsor the tax.